1. Field of the Invention
This invention relates to communication networks.
2. Description of the Prior Art
The modern Internet includes an interconnection of both wireless and wireline networks. In the case of wireless networks, mobile nodes, such as a mobile telephone, require a mechanism for maintaining contact and registration with the network as the mobile node moves through different access and attachment points in the network. In addition, as the mobile node moves to different access and attachment points, the network needs to be able to properly identify and forward calls to the mobile node.
To facilitate this process network protocols, such as the Internet Protocol (IP) version 6 (i.e., Ipv6), promulgated by the Internet Engineering Task Force have been established. Ipv6 or “mobile IP,” as it is often referred to, is intended to enable mobile nodes to move from one attachment point in a network to another attachment point in the network. As such, mobile IP is a communication protocol, which enables the mobile node to communicate from different attachment points and serves as a mechanism for the network to identify and communicate with the mobile node as the mobile node moves to different attachment points in the network.
Mobile IP is designed for use across homogeneous medias as well as heterogeneous media. For example, mobile IP facilitates attachment from one Ethernet segment to another as well as attachment from an Ethernet segment to a wireless Local Area Network (LAN), etc.
A number of architectural components have been defined in the mobile IP protocols, such as Request For Comments (RFC) 3344, published August 2002 by the Internet Engineering Task Force. Notable components include a mobile node, a home agent, and a foreign agent. A mobile node is defined as a host or router that changes its point of attachment from one network or sub-network to another. A mobile node may change its location without changing its IP address. The mobile node may continue to communicate with other Internet nodes from different locations using its constant IP address, assuming connectivity to a point of attachment is available.
A home agent is defined as a router on a mobile node's home network, which tunnels datagrams for delivery to the mobile node when the mobile node is away from home and maintains current location information on the mobile node. A foreign agent is a router on a mobile node's visited network, which provides routing services to the mobile node while registered. The foreign agent detunnels and delivers datagrams to the mobile node that were tunneled by the mobile node's home agent. For datagrams sent by a mobile node, the foreign agent may serve as a default router for registered mobile nodes. As defined in RFC 3344, when the mobile node is away from home, it registers its “care of address” with its home agent. Depending on its method of attachment, the mobile node will register either directly with its home agent or through a foreign agent, which forwards the registration to the home agent.
In addition, RFC 3344 defines a dynamic home agent discovery procedure, in which a mobile node discovers a home agent during the registration process. RFC 3344 refers to this discovery process as “dynamic home agent address resolution.”
In the first step of the dynamic home agent address resolution procedure, the mobile node sends a mobile IP registration request message with a home agent field located in the registration request message set to the network broadcast address of its home network. The receiving home agents on the home network send registration reply messages to the mobile node with an error code 136. In the registration reply messages, the home agents insert their unicast IP address in the home agent field. In the second step of the process, the mobile node selects one home agent and sends a new registration request message to that home agent with the home agent field in the registration request message set to the unicast IP address of a specific home agent.
This conventional registration process is inefficient in wireless networks. In addition, the current method of registration includes a number of shortcomings. For example, 1) a mandatory double roundtrip is required to accomplish registration with the conventional registration process; 2) all the home agents receiving the initial registration request message must respond with an error code 136. The overhead to carry these registration reply messages from a variable number of home agents may become significant over a wireless network link and use the limited radio resources that are available in a wireless network; 3) prior to the completion of the registration process, the mobile node and the applications running on the mobile node cannot start to use other intended services, the resulting delay may be critical for certain services; 4) the processing overhead for the mobile node is high when too many home agents respond to the initial registration request message; and 5) there is no control over which home agent the mobile node chooses for registration; as a result, it is difficult for a network operator to perform load balancing in the network.
Thus, there is a need for a new method and apparatus for performing registration in a mobile IP environment. There is a need for a method of reducing the roundtrip communication required by the current mobile IP registration process. There is a need for a method of minimizing the use of valuable radio resources in the current mobile IP registration process. There is a need for a method of reducing the delay in the current mobile IP registration process. There is a need for a method of reducing the processing overhead of the mobile node when registering with a home agent. There is a need for a mobile IP registration process that facilitates load balancing in the network.